Abstract 936: Gender Differences in the Vasoconstrictor Effect of Sympathetic Neural Activity
Background: Sympathetic activation and its vasoconstrictor effect have been associated with myocardial infarction (MI) and hypertension (HT). However women, when compared to age-matched men, are considerably less likely to develop MI or HT until much later years when the gender gap in incidence tends to diminish. This study was therefore planned to determine whether the vasoconstrictor effect, over a normal range of sympathetic neural activity levels, is different in women compared to men.
Methods: We examined non-obese normal women (34) and men (34). The 2 groups (Table⇓) were matched for age, heart rate (HR), body mass index (BMI) and waist circumference (WC). Muscle sympathetic nerve activity (MSNA) was measured by microneurography from the peroneal nerve and quantified in terms of bursts per 100 cardiac beats (b/100b). Calf blood flow (CBF) was measured simultaneously by plethysmography and expressed in mL 100 mL-1 min-1 (F/V).
Results: Men had greater MSNA (p<0.0008; unpaired t-test), greater mean arterial pressure (MAP) (p<0.02), and similar CBF relative to women. However, within-subject analysis showed that MSNA was negatively correlated to CBF (r=−0.43, p<0.006) in men but not in women.
Conclusion: The results indicate that there is a gender-related difference in the vasoconstrictor effect of sympathetic neural activity encountered in middle-aged normal subjects, with women having a relatively attenuated vascular response to increases in sympathetic activity. These findings may go some way to explaining gender-related differences in the incidence of cardiovascular disease.